Codes and Standards
In addition to the plumbing codes, swimming pool construction and operation are typically governed by Illinois Department of Public Health Regulations (IDPH) and the requirements of local authorities. Publications by the Association of Pool and Spa Professionals (APSP), National Swimming Pool Foundation (NSPF), NSF International (NSF), and Underwriters Laboratories (UL) are often-referenced standards. The Codes typically govern circulation rates, filtration rates for various types of filters, and the spacing of main drains, in addition to maximum velocities through main drain grate-free areas.
The Virginia Graeme Baker Pool and Spa Safety Act (P&SS Act) sets stringent requirements on main drain sizes, velocities, and piping configurations in addition to testing protocols to be regulated according to ASME A112.19.8: Suction Fittings for Use in Swimming Pools, Wading Pools, Spas, and Hot Tubs.
Drain and Grating
At a minimum, all main drain covers and grates shall be a compliant cover or grate bearing the P&SS Act stamp provided by the manufacturer or be field-certified by a licensed professional engineer attesting to its compliance with ASME A112.19.8. In cases where a single main drain is direct-connected to the pump suction, some form of automatic vacuum release or some form of piping that provides an air break to prevent suction entrapment is required.
Filtration
The filter component of a pool system mechanically removes debris from the pool water. The basic media types are used in filters: sand, diatomaceous earth and perlite. Measurable removal efficiency differences exist between the various types. In selecting a filter type, consideration shall be given to the following items:
- Equipment room floor space and ceiling height
- Availability of backwash replacement water
- Filtration efficacy (turbidity of water leaving the filter)
- Water and sewer costs for replacement water
- Ability to handle a possibly large volume of backwash water
- Cost of heating replacement water
- Ease of operation
- Equipment longevity
- Budget requirements
Circulation
Circulation pump selection shall be based on the ability of the pump to move the required amount of water through the circulation and filtration system under worst-case conditions. As the filter becomes dirty (loaded), it restricts flow. As piping ages and becomes calcified, it also can substantially restrict flow.
For these reasons, many Codes mandate that a pump be selected with a design performance point of the minimum flow required, with an available total dynamic head (TDH) capability of 70 to 80 feet. In the absence of such a code requirement, the designer shall assume the expected pressure drop through a dirty filter, usually 15 to 20 pounds per square inch (psi) (103.4 to 137.9 kPa).
Pool Heating
The basic types of heating systems are gas-fired water heaters, steam/hot water heat exchangers, and, infrequently, electric heaters. One possible disadvantage of using heat exchangers is that they require year-round operation of a boiler (if the pool is a 12-month operation). The remainder of the facility may not require the use of the boiler, which may make the case for the use of a supplemental electric heater. Solar Thermal Heating systems may be considered for pool heating. Refer to Mechanical Narrative for Solar Thermal design approach for Pools.
Venting capabilities, (both in the Pool area and Pool Mechanical Spaces) corrosive ambient air, and equipment space requirements are the primary issues to be given consideration. Many facilities are designed with dehumidification systems that use the heat of condensation to heat the pool water or pool space.
Heat Recovery Systems
In an effort to conserve energy and utility usage, a heat recovery system may be used to pull heat from a source of system exhaust or discharge and use that heat to warm the pool water. This is typically done by selection of a specialized Pool Dehumidification Unit that has an integral heat exchanger for this purpose.
Freshwater Makeup
Freshwater makeup may be accomplished by an operator regularly checking the pool water level and turning on the manual freshwater fill valve until the pool is filled properly. Most codes require a skimming action to take place constantly, and a good way to ensure this is to provide some form of automatic freshwater makeup system.